1. Field of the Invention
The present invention relates to a system for detecting whether an object exists or not by utilizing electromagnetic waves and more particularly, to a system for discriminating whether or not the detected object is an animal, including a human. This system may be used as a vehicular front monitoring system for measuring a distance to an object existing ahead of the vehicle.
2. Description of Related Art
Hitherto, as a monitoring system of this sort, there have been systems of shooting a scene ahead of a vehicle by a camera and processing its image to discriminate an object existing ahead of the vehicle and of emitting laser beams or electromagnetic waves such as radio waves ahead of the vehicle to detect the wave reflected by an object existing ahead of the vehicle. Their ordinary purpose is to detect a distance to a preceding vehicle going ahead of the vehicle or an obstacle existing ahead of the vehicle. They can detect an object existing ahead of the lane of the vehicle and measure a distance to the object accurately on motor ways such as highways where pedestrians and bicycles are prohibited and which are standardized.
However, on ordinary roads, there are pedestrians and bicyclers who are coming and going on or near the road surface where vehicles travel or who try to cross the road. Further, even on a motor way, there is a case when a car stops at the road side to pick up or discharge passengers or when construction workers work there. Animals also often prowl on mountainous roads. It is hard to pedestrians, animals and bicyclers traveling adjacent roads especially in the night time. Hereinafter, man and other animals will be expressed simply as animals.
There has also been proposed a front monitoring system for sensing an animal by using an infrared camera. However, because the infrared camera senses infrared rays emitted from warm objects, it also reacts to road lamps, a head light of a vehicle running in the opposite direction, a muffler and tires of a vehicle running ahead. Then, highly advanced shaped recognition technology or motion recognition technology must be combined with it in order to discriminate animals singularly, so that the monitoring system becomes costly. Furthermore, its discriminating accuracy is relatively low.
Although animals reflect radio waves whose wavelength is short and it is possible to detect reflected waves from animals, it is difficult to detect animals, e.g., a pedestrian, singularly because the intensity of the reflected wave from a metal having a high electrical conductivity is greater.